The present invention relates to a high frequency module and a receiver applicable to a television tuner and the like.
In recent years, a television (TV) tuner as exemplary high frequency module has been incorporated not only in a TV receiver but also in an IT device such as personal computer (PC).
The receiver is configured as a so-called double-tuner receiver mounting a terrestrial tuner and a satellite tuner for enabling terrestrial television broadcast and satellite television broadcast to be received.
FIG. 1 is a block diagram showing an exemplary structure of a typical double-tuner broadcasting receiver applied to an IT device.
A receiver 1 in FIG. 1 has a satellite tuner 2, a terrestrial tuner 3, an input terminal 4, a splitter 5, a PCI-Express bridge 6, a power supply 7, a memory 8 and a card edge connector 9.
FIG. 1 shows an exemplary application in a PC using a computer interface called PCI-Express.
A circuit in the structure is standardized in its height to be incorporated into a predetermined slot, and the height needs to be within 3.75 mm.
In the receiver 1, a high frequency signal input from the input terminal 4 is split via the splitter 5 and then is supplied to the two tuners 2 and 3 and decoded to output data.
The data is output to a digital data PCI-Express interface via the PCI-Express bridge 6.
At this time, the power supply 7 supplies a necessary voltage and current and the memory 8 operates to hold necessary storage data.
The double-tuner receiver is required to be downsized and simplified in its mounting design. In order to address the requirements, a receiver in which two tuners are arranged in one double-tuner module is put into practical use.
FIG. 2 is a block diagram showing an exemplary structure of a broadcasting receiver to which a double-tuner module is applied.
In FIG. 2, a receiver 1A has a double-tuner module 10.
The functional parts denoted with the same numbers as FIG. 1 operate in the same way as FIG. 1.
FIG. 3 is a diagram showing a schematic structure of a double-tuner module arranged on a PCI-Express board.
There is exemplified that the double-tuner module 10 is designed on a board 11 to have a height of 2.3 mm.
In this way, a satellite tuner 12 and a terrestrial tuner 13 are mounted as integrated circuits (IC) on the board 11 and are covered with a shield case 14 so that a thin module is configured.
As described above, a more integrated IC is suitable for a semiconductor used for realizing the thin tuner, and the internal satellite tuner 12 and the internal terrestrial tuner 13 in FIG. 3 similarly each incorporate a local oscillator and its inductor for enhancing the degree of integration.
FIG. 4 is a diagram for explaining an exemplary inductor incorporated in an IC.
In a semiconductor operating in a high frequency band, a voltage controlled oscillator (VCO) typically implemented by an external circuit is an on-chip type VCO 21 laid on an IC chip 20 in FIG. 4. An inductor 22 essential for the VCO 21 is realized by an aluminum wiring in a spiral shape having a concentric shape.
The present example is an exemplary IC in which the inductor used for the local oscillator (VCO 21 in the drawing) is configured in pattern layout of the IC in the explanatory diagram of a process called QUBIC4 by NXP Semiconductors.
Typically, the inductor incorporated in the IC is arranged on a plane and thus has a spiral structure in which a concentric circle is spirally rounded as shown in FIG. 4.
Thus, an electric field and a magnetic field induced from the inductor are radiated in the vertically direction on the sheet during the IC operation.
Thus, when multiple ICs each incorporating the local oscillator circuit and the inductor are used, an effect of an electric field occurring around the ICs needs to be considered.
FIG. 5A and FIG. 5B are diagrams showing a concept of an electric field radiated by an IC incorporating an inductor therein.
FIG. 5A shows an example in which a radio wave 31 is radiated from an IC 30 mounted on the circuit board 11.
In this case, the electric field intensity is circular near the IC 30 but is parallel to the radiation surface with a distance from the IC 30 as radiation element.
FIG. 5B shows how the IC 30 is actually mounted on a tuner module.
That is, a copper foil surface 33 is covered with the shield case 14 in the lateral direction and in the top surface direction at the bottom of the IC 30 mounted on the circuit board 11. In this case, since the radiated radio wave 31 is reflected near the shield case 14 and the copper foil surface 33, the circular electric field is propagated via a path 32 while being reflected.
The shield case 14 is made of a metal typically called nickel silver as alloy of copper, nickel and zinc which is a thin material and is excellent in solderability, but any material excellent in conductivity is typically nonproblematic, and a low-cost tin material or its similar materials may be used when a limitation on shape is not severe.
FIG. 6A and FIG. 6B are diagrams showing a concept of a magnetic field radiated by the IC incorporating the inductor therein.
In FIG. 6A and FIG. 6B, the same components as those in FIG. 5 are denoted with the same numerals.
In FIG. 6A, there is formed a loop in which a magnetic field 40 is induced in the upward direction from the IC 30 and returns to the bottom surface.
Similarly, as shown in FIG. 6B, the magnetic field hit on the shield case 14 and the conductor surface of the copper foil surface 33 on the surface of the circuit board 11 generates eddy currents 41. Then, the eddy currents are propagated inside the conductor and diffused therein.
FIG. 7A and FIG. 7B are diagrams equivalently showing propagation of a high frequency signal due to the electric field and the magnetic field in FIG. 5 and FIG. 6.
In FIG. 7A, when the shield case 14 is present near the top surface of the IC 30, the electric field and the magnetic field replace the propagation of a signal due to reflection or current induction via the case with a stray capacitance 50.
FIG. 7B is an explanatory diagram in which the stray capacitance is applied to the double-tuner module in FIG. 3, and shows how the satellite tuner 12 and the terrestrial tuner 13 are connected with each other via the stray capacitance 50.
It can be easily understood that the inductor incorporated in the IC 30 is also an element for generating an electromagnetic field when a current is flowed similarly to typical components, and conversely is an element for inducing a current in the electromagnetic field.